No abstract

No abstract

In this paper, a practical method is proposed for the efficient solution of fluid power systems with singularities originating (in particular) from the presence in the system of small volumes. The method is based on the use of an enhanced version of the pseudo-dynamic solver (the advanced pseudodynamic solver), which seeks the steady-state solution of pressure building up in the small volume. This solver can be attributed to the class of explicit solvers. There are two main advantages of the proposed solver. The first is the higher accuracy and numerical stability of the solution compared with the classical pseudodynamic solver, owing to the enhanced solver structure and the use of an adaptive convergence criterion. The second is the faster calculation time compared with conventional integration methods such as the fourth-order Runge-Kutta method, owing to the obtained possibility of larger integration time step usage. Thus, the advanced pseudo-dynamic solver can become a preferred method in the simulation of complex fluid power circuits. Simulation results of the C code implementation confirm that the advanced pseudo-dynamic solver is better than conventional solvers for the solution of the real-time systems that include fluid power components with small volumes.

The work addresses the problem of the fast and accurate calculation of the mathematically stiff hydraulic models using the modified pseudo-dynamic solver (PDS). In particular, it studies which of the numerical integration methods inside the modified PDS ensure efficient calculation of the stiff hydraulic model. In the work, the operating principle of the modified PDS is described. The effect of the three different fixed-step integration methods (Euler, Runge-Kutta of fourth order, and modified Heun’s method) are considered. The numerical stability of the modified Heun’s method is improved by substituting the purely turbulent orifice model with the two-regime orifice model. The two-regime orifice accounts for both the turbulent and laminar flows and thus allows to avoid the numerical problems related to the small pressure drops. As a numerical example of the mathematically stiff hydraulic model a hydraulic circuit with the two-way flow control valve which contains small volume is employed. As the implementation environment for the developed simulation models the compiled C language that supports the real-time simulation is chosen. The solutions obtained for the numerical example using the modified PDS based on the three integration methods, their accuracies and calculation speeds are presented in comparison with the solution obtained using conventional integration procedure. The obtained results show that, in general, the modified PDS allows to solve numerically stiff hydraulic models in a very efficient way ensuring accelerated simulation with the high solution accuracy. It is also shown that the simulation speed-up can be obtained not only by the complexity reduction of the numerical integration method employed inside the modified PDS but also by increasing its numerical stability.

No abstract